1. Field of the Invention
The present invention relates to a canal+decoder switching circuit for video cassette recorders, and more particularly to a canal+decoder switching circuit for VCRs for receiving SECAM (sequential technique and memory storage) system broadcasts, which enables a canal+decoder for receiving a canal+broadcast signal to be used not only in VCR mode but also in television (TV) mode.
2. Description of the Prior Art
In the SECAM system broadcasts, the canal+broadcast signal is dissimilar to a mormal broadcast signal. The canal+broadcast signal is transmitted in such a way that each video signal for each successive line has different phase delay with each other and is converted into a normal broadcast signal by the canal+decoder in a receiver in order to obtain a clean picture.
As the cannal+decoder is provided with secret codes, TV stations makes such secret codes known to the general televiewers who possess canal+decoders every month and the televiewer who is ignorant of such secret codes is unable to catch the canal+broadcast because the decoder fails to achieve exact decoding. Thus, a canal+decoder is positiely necessary to receive canal+broadcasts successfully.
In the conventional VCRs for receiving the canal+broadcasts, an exclusive jack is provided so that the canal+decoder is connected thereto. Thus, when a canal+broadcast channel is selected, the output of the demodulator of the VCR is connected to the input of the canal+decoder and the canal+decoder converts the demodulated canal+signal into the normal signal. At this time, the canal+decoder outputs a high ievel signal through its control signal output only when the canal+signal is perfectly converted into the normal signal and then the converted signal is provided to the video signal processing circuit of the VCR in response to the control signal of high level, resulting in that the canal+broadcast signal can be received in VCR mode.
On the other hand, if the canal+decoder is connected to a TV, the canal+broadcast signal can be received in TV mode in the same manner as described above.
However, in the conventional VCR associated with the TV, the canal+decoder is usually connected only to the VTR. Thus, it is unable to obtain a normal picture when the televiewer intends to receive the canal+broadcast in TV mode. Although it is possible to obtain a normal picture when the canal+decoder is separated from the VCR and connected directly to the TV, such work is troublesome and inconvenient.